1. Field of the Invention
The present invention relates to a miniature stacked microstrip antenna of wide band in radio communication apparatus.
2. Description of the Prior Art
Conventionally, a standard microstrip antenna consists of a ground plane, a radiating element and a dielectric layer sandwiched between them. When a high-frequency voltage is supplied between the ground plane and the radiating element, the antenna has a resonance frequency decided by an effective wavelength (.lambda.) in the dielectric layer. In this case, the radiating element is formed by a square having a side of .lambda./2.
Furthermore, a microstrip antenna which short-circuits one whole edge of the radiating element with the ground plane in the standard microstrip antenna is known. The microstrip antenna can get the same resonance frequency as that of the standard microstrip antenna with an open area which is 1/2 or less.
With the antennas as stated above, the resonance frequencies are determined by the dimensions of the radiating elements and the dimentions between the ground plane and the radiating elements.
Therefore, the antennas have the disadvantage that it is difficult of being made still smaller in size as may be needed. Specially, the antennas become a large open area when they need a low resonance frequency.
As another disadvantage, in a case where deviations have occurred between designed resonance frequency and the resonance frequency of the fabricated antenna, the dimension of the radiating element must be changed, and the correction of the resonance frequency is difficult.